The bearing used in a ship’s stern tube plays an important role in determining how well it performs in open water.
First and foremost, by enclosing the propeller shaft in a low–friction casing, the bearing has a big say in how well the power generated by the engine is converted into torque and thrust.
The stern tube bearing also does a lot of the heavy lifting when it comes to keeping the propeller well-aligned, helping to reduce vibration and dampen noise.
These are just a couple of the ways a bearing helps improve performance.
In this post, we take a closer look at just how a stern tube bearing boosts the performance of any boat or ship across a range of metrics.
Fuel Efficiency
In large part, a sea-going vessel’s performance depends on how efficiently it can use the fuel available to it.
Given that waterborne vehicles depend on propellers to move, this means all boats and ships need to be able to efficiently convert energy from the engine into thrust through the blades of the propeller.
A bearing plays a big role here, as its main job is to help reduce the friction that naturally arises as the propeller turns in the stern tube.
Nowadays, friction reduction is achieved in clever ways, not simply by introducing a lubricant like oil into the stern tube to keep it as friction-free as possible.
For example, Tenmat stern tube bearings use innovative fibre bonded with resin materials together with friction modifiers like molybdenum disulphide to achieve frictionless sailing.
Low Stick-Slip
It takes a huge amount of power to get a boat started. After all, the propeller has to overcome a substantial inertial force when the propeller is at rest.
A stern tube bearing coupled with an effective lubrication system featuring innovative frictionless material can substantially reduce the energy required to start the propeller, meaning the engine works less hard and consumes less fuel.
This also means you avoid the nasty stick-slip judder you get with a misfiring propeller as it tries to overcome static friction when the engines kick.
Thermal Stability
Friction produces a lot of heat, and heat will deform a metal bearing if it reaches high enough temperatures.
Naturally, a deformed propeller shaft isn’t going to operate to its potential.
Tolerances
Modern bearings, manufactured from clever composite materials and set in reticulated (matrix) structures, afford them high strength, dimensional stability, and the ability to withstand heavy pressures from the propeller shaft without deforming.
This is now always the case with traditional bearings – for example, ones manufactured from an elastomeric (rubber) material often require large tolerances as they tend to swell up when submerged in water and wear quickly in turbid water.
Small but significant improvements in a bearing’s tolerance can drive substantial performance improvements, as a snugger stern tube bearing occupies less space and therefore contributes less weight to a ship’s tonnage.
Conclusion
It’s difficult to overstate how important a stern tube bearing is to the performance of a sea-faring vehicle.
By opting for the right bearing, a ship or boat operator can squeeze gains across all the metrics that matter.
